In vitro efficacy of ribavirin against canine distemper virus

Despite vaccination, canine distemper virus (CDV) remains one of the important pathogen of dogs with worldwide distribution. Ribavirin (RIB) inhibits replication of measles virus (MV), a morbillivirus closely related to CDV, both in vitro and in vivo: In this report the antiviral activity of RIB against CDV in cell cultures was assessed. Quantitative real-time RT-PCR was used to measure viral RNA in VERO cell infected by CDV and to evaluate the inhibitory effects of RIB. RIB caused a dose- and time dependent decrease in accumulation of CDV RNA when added after virus adsorption. RIB was highly effective in preventing replication at low concentrations with 50% virus-inhibitory concentration ranging from 0.02 to 0.05 mM. Such low level values were comparable to values displayed by highly susceptible strains of MV. In addition CDV was passaged sequentially in VERO cell monolayer in the presence of RIB to trigger viral extinction. The virus was no longer detected after three passages, suggesting that error catastrophe is one of the modes of action of RIB against CDV. These finding suggest RIB as a promising tool for the therapy of CD in dogs.